Incineration, an attractive alternative to burying for the disposal of urban garbage, is practiced throughout the world and results in a considerable decrease in waste volume and the recovery of energy in the form of steam or electricity. One of the significant drawbacks to the incineration procedure is that several hundred stable and toxic compounds, including polychlorinated dibenzodioxins (collectively commonly termed "dioxins") and polychlorinated bidenzofurans, are formed and are present in parts-per-million concentrations both in the flyash formed during combustion and in the stack emissions.
A large city may incinerate 3 to 5 million tons of garbage annually. For every million tons of urban waste incinerated, about 34,000 tons of flyash are produced by the typical incinerator. Between 95 and 99% of the flyash is precipitated electrostatically and buried in landfills. The remainder is emitted from the incinerator stack along with the gaseous by-products, namely water vapor, HCl, CO.sub.2, air and volatilized organic compounds. The gaseous stack emissions introduce dioxins to the atmosphere and landfill disposal of flyash introduces dioxins into the earth, from where they my be leached into water systems.
The primary hazard of dioxins to humans may be cancer in the long term, but dioxins exert a much larger impact on the general environment and are considered undesirable. There exists, therefore, a need for a means to decrease the dioxin content of both solid and gaseous by-products from incinerator systems.